Recently, diagnostic endoscopic techniques have been developed to irradiate tissue to be studied with visible light and to detect resulting fluorescent images which are then analyzed for diagnostic purposes. These techniques have been found particularly useful for diagnosing disease conditions such as cancers or tissue degeneration and for highlighting the boundary regions of such conditions under study. These techniques are sometimes enhanced by also studying normal light images resulting from reflection of the irradiating visible light (usually white light).
In the case of autofluorescence, i.e., the stimulated emission resulting from impingement of the excitation light onto a biological tissue, the fluorescence typically has a longer wavelength than that of the excitation light. Fluorescent substances within organisms are exemplified by collagens, NADH (nicotinamide adenine dinucleotide), FMN (flavin mononucleotide), pyridine nucleotide and the like. Recently, the relationship between such fluorescent substances and various diseases has been recognized, making it possible to diagnose cancers and the like by use of these fluorescences.
In addition, certain fluorescent substances such as HpD (hematoporphyrin), Photofrin, ALA (delta-amino levulinic acid), and GFP (Green fluorescent protein), are selectively absorbed by cancers and thus may be used as contrast materials. In addition, certain fluorescent substances may be added to a monoclonal antibody whereby the fluorescent may be attached to affected areas by an antigen antibody reaction.
Lasers, mercury lamps, metal halide lamps, xenon lamps, and the like may be used as and for the excitation light, which may be of a certain frequency or frequencies or may cover a certain spectrum that is useful for Autofluorescence (“AF”), Photodynamic Diagnosis (“PDD”), Indocyanine green (“ICG”), or other such known diagnostic techniques. For example, when a light with the wavelength of 437 nm is emitted onto a gastrointestinal tract tissue, green autofluorescence by abnormal tissues is attenuated compared to the autofluorescence of normal tissues, but red autofluorescence of abnormal tissues is not attenuated as much compared to the autofluorescence of normal tissues.
Since the fluorescent images obtained in this way typically have very low reflective intensities as compared to the reflected images obtained with conventional white light, photomultiplication, such as by using a higher camera system gain factor or increased imager integration time, may be necessary.
Generally, when a blue or ultraviolet light is emitted onto biological tissue, an autofluorescence occurs within a longer wavelength band than that of the excitation light. Moreover, fluorescent spectra are different between normal tissues and abnormal tissues, such as precancerous tissues, cancerous tissues, inflammatory tissues and dysplastic tissues, such that the existence of lesions and conditions of lesions can be detected based on subtle changes in coloration of the fluorescent images.
In particular, since with a blue excitation light, the intensity distribution of fluorescence stimulated near the green region (especially that of 490 nm-560 nm) is stronger in normal tissue than in diseased tissue, emissions in the green region and in the red region (e.g., wavelengths in the 620 nm-800 nm region) are arithmetically processed to generate two-dimensional fluorescent images, and by these fluorescent images the discrimination between abnormal and/or diseased areas and normal areas can be achieved.
In known systems, video images are produced for diagnostic observation of autofluorescent emissions, and adjustments are made to the ratio between the video signals corresponding to the green and red fluorescent intensities to allow normal tissues to have a certain color tone. Accordingly, tissue known to be normal is first observed, and the ratios of the red and green emissions are adjusted to establish a reference color tone. Then, after the adjustment of the color tone of the normal parts, the potentially diseased tissue is observed. In this way, the normal parts are designated with a certain color tone and abnormal parts are designated with different color tones from that of the normal parts due to the attenuation of the green signal. By the differences in color tones between abnormal and normal parts, the abnormal parts can be visualized. Typically, the ratio is adjusted so that the normal tissue appears in a cyanic color tone and diseased tissue appears as a red color tone.
Moreover, in some fluorescent observation devices, a single light source is used both as an excitation light to conduct fluorescent observations and as a white light to conduct white light observations by insertion and removal of a color filter, either by mechanical or electronic means. As will be understood, when only fluorescent images are desired, there should be no illumination by, or detection of, white light, but only illumination by and detection of the excitation light. Thus, switching is required so that when a white light image is to be obtained, a white light is emitted and/or detected, and when a fluorescent image is to be obtained, an excitation light is emitted and/or detected.
Further, image switching is typically controlled so that when white light is emitted the resulting image is provided only to a white image imaging device, and so that when the excitation light is emitted, the fluorescent image is provided only to a high-sensitivity fluorescent imaging device.
Generally, since the subtle variations in coloration of fluorescent images are subjectively visualized by a medical practitioner, the lack of fixed discrimination standards makes it difficult to compare findings by different practitioners, and at different medical facilities.
Also, because adjustment of color tone for normal tissue is conventionally performed and dependent upon the individual judgment of the medical practitioner, the absence of fixed calibration standards renders objective diagnosis by color tone difficult if not impossible. Resultantly, comparison of the white light image against the excitation light image may be the most accurate means to discriminate diseased from healthy tissue. To accomplish this discrimination, switching back-and-forth between white light and excitation light images is advantageous. The switching becomes more critical in a therapeutic environment. If diseased tissue is discovered, the medical practitioner may need to excise the tissue while switching between the two images to ensure all diseased tissue has been removed.
Further, due to conventional fluorescence diagnosis endoscope system construction described above, only the light produced by the fluorescence of tissue is detected by the imager element of the endoscope. Thus, suspect tissue cannot be observed when illuminated with white light by the same endoscope. In some instances, to examine suspect tissue using white light, the endoscope designed for fluorescence diagnosis is removed and another endoscope for normal observation is inserted. This is time consuming, disruptive, and potentially hazardous to a patient during an examination and/or surgical procedure.
Various display schemes relating to differentiating normal tissue from diseased tissue are known. Generally, these display schemes fall into 4 categories:
1. Diseased tissue view and normal tissue view displayed combined/superimposed within a single video frame.
2. Diseased tissue view and normal tissue view displayed combined/superimposed with alternating video frames.
3. Diseased tissue view and normal tissue view displayed separately within a single video frames.
4. Diseased tissue view and normal tissue view displayed separately within alternating video frames.
Depending upon how the excitation-light is generated and/or detected, this switching requires that a light source switch between a “white-light” mode and “excitation light” mode, and can be initiated from the CCU (from a camera head button, for example).
Regardless of how the excitation light image is produced, either superimposing the excitation light image over the white light image, or a side-by-side composite image, is typical. For example:
U.S. Pat. No. 4,556,057 to Hiruma et al. relates to a cancer diagnosis device which selectively illuminates a cancer focus with white light and laser light synchronously with an imaging device, images of which are coupled to a spectroscope for detecting spectral response.
U.S. Pat. No. 4,699,125 to Komatsu relates to storing superposed frames from an endoscopic video in response to a freeze instruction, photographing a frozen image displayed on a display means, and sequentially comparing image signals for a predetermined color component in order to obtain a clear frozen image through motion detection.
U.S. Pat. No. 4,768,513 to Suzuki relates to analyzing fluorescence wavelength patterns for diagnostic purposes.
U.S. Pat. No. 4,791,480 to Muranaka relates to an endoscope having an adjustable light source which can be used to produce video and still images. When a still image is taken, the illuminating light can be pulsed during frame transfer from the solid state camera element in order to avoid producing a blurred image.
U.S. Pat. No. 4,821,117 to Sekiguchi relates to alternately irradiating an object with visible and excitation radiation and controlling the irradiating, storage, and displaying means to simultaneously display a visible radiation image and a fluorescent image.
U.S. Pat. No. 4,885,634 to Yabe relates to simultaneously displaying a color image and a specific wavelength image on separate monitors or on the same monitor screen.
U.S. Pat. No. 4,930,516 to Alfano et al. relates to exciting a tissue with monochromatic lights and measuring the intensity of visible native luminescence emitted from the tissue of at least two wavelengths, and displaying a signal corresponding to the ration between the intensities of at least two wavelengths.
U.S. Pat. No. 5,034,888 to Uehara et al. relates to an electronic endoscope apparatus having different image processing characteristics for a moving image and a still image.
U.S. Pat. No. 5,507,287 to Palcic et al. relates to sending first and second spectral band autofluorescence images to the red and green channels of an RGB video monitor to create a combined display image.
U.S. Pat. No. 5,590,660 to MacAulay et al. relates to sending autofluorescence and remittance light images to the red and green channels of an RGB video monitor to create a pseudo-color image.
U.S. Pat. No. 5,646,680 to Yajima relates to displaying either an endoscope video signal either through a peripheral device or directly so that the peripheral device can be bypassed in case of a malfunction.
U.S. Pat. No. 5,647,368 to Zeng et al. relates to collecting color filtered excitation light and autofluorescence light and sending the images to the red and green channels of an RGB video monitor to create a false color contrast image.
U.S. Pat. No. 5,749,830 to Kaneko et al. relates to switching display between simultaneous display and time-divided display of normal observation video and fluorescent observation video.
U.S. Pat. No. 5,827,190 to Palcic et al. relates to storing and combining sequential autofluorescence and reflectance images for simultaneous display as a pseudo-color image.
U.S. Pat. No. 5,986,271 to Lazarev et al. relates to displaying a superimposed or first and second region view of both a full color and resulting autofluorescence image.
U.S. Pat. No. 6,028,622 to Suzuki relates to displaying superimposed fluorescent images under different excitation lights.
U.S. Pat. No. 6,099,466 to Sano et al. relates to displaying a color image and/or a fluorescence image produced by processing fluorescence filtered image signals.
U.S. Pat. No. 6,192,267 to Scherninski et al. relates to an angiography device for displaying contrast enhanced fluorescence images.
U.S. Pat. No. 6,293,911 to Imaizumi et al. relates to simultaneously displaying an image under autofluorescence and white light in superimposed or side-by-side format, and where a second image signal can be subtracted from a first image signal.
U.S. Pat. No. 6,364,829 to Fulghum relates to display of sequentially or simultaneously detected fluorescence and reference images.
U.S. Pat. No. 6,422,994 to Kaneko et al. relates to superimposing a tissue fluorescence image color interpretation guide and an enhanced fluorescence image video.
U.S. Pat. No. 6,603,552 to Cline et al. relates to superimposing reflected light and fluorescence images.
U.S. Pat. No. 6,899,675 to Cline et al. relates to displaying superimposed video images from pixels of a low light color image sensor having one or more color filters.
U.S. Pat. No. 7,420,151 to Fengler et al. relates to simultaneously displaying a white light and short-wavelength light image.
U.S. Pat. No. 7,965,878 to Higuchi et al. relates to an endoscopic system that stores matrix data for forming a spectral image and forms a spectral image in a selected wavelength band according to a matrix operation on an original still image. The original still and one or more spectral images can then be displayed.
However the use of video having superimposed, interleaved, or side-by-side diagnostic and normal views as described above can be confusing and lack clarity in many circumstances.
It is therefore desired to provide a device which addresses these deficiencies.